Field of the Invention
The present invention relates to an object detecting apparatus for emitting a transmission wave toward an area in which an object to be detected may appear, and for detecting the distance up to the object based on a reflection wave that is the transmission wave reflected from the object.
Description of the Related Art
According to Japanese Laid-Open Patent Publication No. 2009-222445 (hereinafter referred to as “JP 2009-222445 A”), an object of the disclosed invention is to provide an ultrasonic distance sensor system for measuring the distance up to a short-range object highly frequently with a single sensor having a wide measurement range (see paragraph [0005], Abstract). To achieve this object, according to JP 2009-222445 A, the ultrasonic distance sensor system includes a transmitting device 2 for transmitting ultrasonic waves toward an object, a driving circuit (microcomputer 16) for outputting a drive signal to the transmitting device 2, a receiving device 3 for receiving reflection waves from the object, and a signal processing circuit (microcomputer 16) for detecting the distance up to the object based on a signal from the receiving device 3. The signal processing circuit generates transmission waves based on a plurality of transmission patterns, and calculates the distance up to the object based on a correlation between the transmission patterns and the signal from the receiving device 3 (see Abstract).
Further, according to JP 2009-222445 A, the ultrasonic distance sensor system performs a short-range distance measuring process and a long-range distance measuring process concurrently based on a plurality of transmission signal patterns. More specifically, the ultrasonic distance sensor system generates a transmission signal pattern having a shorter period in the short-range distance measuring process, as well as a transmission signal pattern having a longer period in the long-range distance measuring process (see paragraph [0013], FIG. 2).
Although JP 2009-222445 A reveals a short-range distance measuring process and a long-range distance measuring process using ultrasonic waves, the reference does not address the detection of failures in the ultrasonic sensors. There are instances in which multiple ultrasonic sensors are used in a vehicle for ensuring fail-safe operation of the vehicle. However, JP 2009-222445 A is silent concerning the detection of failures in the case that a plurality of ultrasonic sensors are used. Detection of failures generally is required not only for such ultrasonic sensors, but also is required in connection with a transmission and reception unit, or a contactless range detection sensor including a transmitter for emitting transmission waves and a receiver for receiving reflection waves produced in response to the transmission waves.